Writer's lecture will show new lens on humanity's past

Published 5:30 am, Tuesday, April 10, 2007

Nicholas Wade is the author of Before the Dawn: Recovering the Lost History of Our Ancestors.

Nicholas Wade is the author of Before the Dawn: Recovering the Lost History of Our Ancestors.

Photo: NAUM KAZHDAN, NEW YORK TIMES

Writer's lecture will show new lens on humanity's past

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Nicholas Wade, a New York Times science writer, has had a front-row seat for the dawning of the genomic age. He's covered the Human Genome Project and nearly every other facet of DNA research.Wade has followed the striking insights DNA has given researchers into the depths of the human past, from anthropology to linguistics. He's in Houston to speak tonight as part of the 2007 Leakey Speaker Series on Human Origins.He recentlyspoke with Chronicle science writer Eric Berger to talk DNA and archaeology.

Q: You're coming to Houston to speak about DNA and how it has provided a new lens upon humanity's past. What has DNA taught us in recent years that fossils could not?

A: It's filled in a lot of detail, especially about our recent evolutionary history in the last 50,000 years. The fossils trace the period from about 5 million years ago until about 100,000 years ago, but they can't really tell us anything about the history or nature of our society. DNA is really good at filling in many of those gaps.

Q: Hasn't DNA also been useful for more ancient human prehistory, such as determining precisely when the human and chimpanzee ancestors split on the evolutionary tree?

A: Oh that's certainly true, and the reach of DNA goes almost as far back into the past as you would care to look. But it also does provide insights into the most recent 50,000 years that are available by no other means.

Q: Such as?

A: I think one of the most evocative is that of the date when we first started to wear clothing, which can be figured out from the DNA of the body louse, which evolved from the head louse at the time we first started to wear tailored clothes. This is something archaeologists have always tried to get a fix on, but they never can because clothes and the needles used to sew them are very perishable. So archaeologists could never say when we began to wear clothes. But now, from DNA, a fairly precise date has emerged (Berger note: Around 72,000 years ago).

Q: That was quite unexpected, wasn't it? If you'd asked an archaeologist a few years ago if lice would be important in determining when humans first wore clothing, you might have been laughed at.

A: That's probably right. Another big surprise that has come out of DNA is the fact that our evolution did not come to a halt at some point in the very distant past, but has rather continued rigorously throughout the 50,000 years of recent history. This is a surprise to many historians and archaeologists who always assumed that evolution is something they don't need to worry about at all.

Q: I'm glad you brought up historians. You talk about the dalliances of Thomas Jefferson in your book Before the Dawn, and there's even been some recent evidence that he might have been Jewish. Do you find that historians have recognized the power of DNA for their own research?

A: I think they realize the power of DNA to settle specific historical issues, like the one you mentioned. But they haven't yet taken onboard the fact that if we've continued to evolve, the past isn't just another country, it's different people. In other words, human nature may have changed in the historical past, and it may have changed in different societies in different ways.

Q: If they were to investigate further in this area, what might they discover?

A: In my book, I argue that the humans of the past were very much more aggressive than we are today. We've become so much less aggressive that, in fact, it was that process that has allowed us to switch from a hunter-gatherer way of life about 15,000 years ago to the first societies. So, settled societies simply aren't possible unless you've developed some way of getting on with your neighbors and living in larger than kin-based groups as our ancestors did for thousands of years previously. So, the very fact that human nature has changed in that respect is something that historians should play close attention to because it may have changed in lots of other ways as well.

Q: DNA seems to have proved useful for identifying when specific changes took place, but what you're arguing here is that we can learn a lot about the "why," too?

A: We're just at the beginning of this field, but we can already see that once you understand what a gene is for, then you can also develop ways of dating when that gene became universal in human population. For example, there's a gene involved in language called the FOXP2 gene, that has emerged from a study of a very interesting family in London, half of whose members have a very subtle defect in their speech. This looks like it was one of the last genes to be put in place as the language faculty was perfected. You can date when that gene became universal in the human population, and it's about 50,000 to 100,000 years ago.

Q: We can know, then, when humans began to speak to one another?

A: Yes, and there will be lots of other genes — for example, changes in skin color — where as soon we identify them and their roles, we will be able to date them and say when this feature was acquired in human evolution.